Add some basic editing facilities

editor-challenge/src/state.rs

@@ -57,6 +57,18 @@ impl AppState {
         KeyCode::Left => {
             self.cursor_left();
         }
+        KeyCode::Backspace => {
+            self.contents.backspace(&mut self.cursor);
+        }
+        KeyCode::Delete => {
+            self.contents.delete_at(&mut self.cursor);
+        }
+        KeyCode::Enter => {
+            self.contents.new_line(&mut self.cursor);
+        }
+        KeyCode::Char(c) => {
+            self.contents.insert_at(&mut self.cursor, c);
+        }
         _ => {}
     };
     }

editor-challenge/src/types.rs

@@ -1,3 +1,7 @@
+
+// TODO: I'm increasingly feeling that cursors are per-document, not per-application. So I think I
+// want to move the cursor into here, and then rendering requires asking for the cursor for the
+// current document.
 #[derive(Default)]
 pub struct Document {
     rows: Vec<String>
@@ -24,6 +28,38 @@ impl Document {
     pub fn row_count(&self) -> usize {
         self.rows.len()
     }
+
+    pub fn insert_at(&mut self, cursor: &mut Cursor, c: char){
+        let (row, column) = cursor.addr();
+
+        self.rows[row].insert(column, c);
+        cursor.cursor_right(self);
+    }
+
+    pub fn backspace(&mut self, cursor: &mut Cursor) {
+        let (row, column) = cursor.addr();
+        if cursor.column > 0 {
+            let _ = self.rows[row].remove(column - 1);
+            cursor.cursor_left();
+        }
+    }
+
+    pub fn delete_at(&mut self, cursor: &mut Cursor) {
+        let (row, column) = cursor.addr();
+        if cursor.column < self.rows[row].len() {
+            self.rows[row].remove(column);
+            cursor.correct_columns(self);
+        }
+    }
+
+    pub fn new_line(&mut self, cursor: &mut Cursor) {
+        // when doing a newline, take everything to the right of the cursor from the current line
+        // and move it to the next line.
+        let (row, _) = cursor.addr();
+
+        self.rows.insert(row, String::new());
+        cursor.cursor_down(&self);
+    }
 }
 
 #[derive(Default)]